Microprocessor than appear in the PART LIST section is ATtiny2313v-10PU but in the picture on same section appear ATtiny2313-20PU.
As I can understand the difference between them is in "MAX clock freq".

Which one of microprocessors should I use?
Can I use any one of them without changing the code?

Parts with a v", like the ATtiny2313v, work at lower voltages, than the ones without the "v": 1.8v instead of 2.7v. That's why the "v" part is better here, since it will keep working, even when the batteries are way weak.

I love your funny projects, and because of the simple board layouts and the high shipping costs to europe I prefer to build these nice things on "Lochraster" PCBs. I want to build me a "Brain Machine".

But here in Germany I found no electronic store that sells Attiny2313V-10, so I have to take the 2312-20 which does not ran with less than 2.7V. As Mitch said, it will run even with 2 AA-Batteries - but it will much more reliable if I take 3 AA-Batteries and run the kit with 4.5V.

But then I have to recalculate the resistors for the LEDs, no? But I don't know very much about electronics, so perhaps for the BrainMachine I have to recalculate the capacitors and resistors for the sound output too, to get the right frequencies? The ISP part / serial programming power adaption part I dont have to touch, no?

I know that this thread hasn't been seen in a while, but I ran into a problem here. I wanted to program my fresh ATtiny2313-20PU on my SpokePOVs using USBtiny, but they get the AVR initilization failed error. However, if I drop in my ATtiny2313V-10PU instead, it connects fine and allows me to flash the SpokePOV Firmware on the same board.